OMERACT magnetic resonance imaging initiative on structural and inflammatory lesions in ankylosing spondylitis--report of a special interest group at OMERACT 10 on sacroiliac joint and spine lesions.

The ASAS/OMERACT MRI group recently described and defined magnetic resonance imaging (MRI) findings in sacroiliac joints (SIJ) that are essential for the diagnosis of sacroiliitis in patients with axial spondyloarthritis, including ankylosing spondylitis (AS). At the Outcome Measures in Rheumatology Clinical Trials (OMERACT) 2010 meeting, a special interest group (SIG) was formed to design a research agenda for the definition and description of structural lesions in the SIJ and the spine in patients with established AS. During the SIG, a summary of the previous work of the group was presented to all participants, containing: (1) a description of the current definitions of structural SIJ changes; (2) available scoring methods for SIJ changes; (3) data from a previous pilot MRI exercise on chronic SIJ changes performed by members of the group; and (4) a proposal for a research agenda for OMERACT 11. The group agreed on the project's scientific merits and the need to evaluate all available scoring methods and to have clear definitions for all possible abnormalities that can be seen on MRI, prior to the start of the exercise. It was also agreed that the exercise should include scoring of both structural and inflammatory lesions, due to lack of agreement about the best scoring method for assessing both types of lesions in AS. Participants agreed that longitudinal MRI over a certain period are needed to learn about the time sequence of pathologic changes and to understand the course of the disease. Finally, participants asked the group to add the development of a scoring method for structural changes in the spine in a subsequent exercise. Further to these objectives, all experts who agreed to contribute in the exercise will collaborate to achieve consensus on definitions and to organize training in the different scoring systems prior to the start of the project, with the aim to finalize the multiple reader exercise by the end of 2011, in time for OMERACT 11.